Fig. 13
From: CT imaging features of atrioventricular shunts: what the radiologist must know
Axial (a) and coronal (b) contrast-enhanced CT images clearly depict an ostium secundum defect (asterisk) at the fossa ovalis with shunting of contrast-enhanced blood from the left atrium (LA) to the right atrium (RA). Contrary to a patent foramen ovale, the flow is perpendicular to the axis of the interatrial septum because of the absence of an overlapping septal flap. In large defects like in this case, this can lead to volume overload and dilatation of the right atrium and ventricle